Andre,
Dry brushing alone is not adequate. Even if your records are perfectly clean, the stylus acquires a thin (molecular) layer of vinyl from each play. If this is not removed regularly it will continue to build up. This can be seen on well-used but uncleaned styli, which slowly go dull or yellow.
If you wish, email me your address and I'll send you some Magic Eraser pieces. Value for customs will be about .001EUR, so it should get through okay!
Search the archives for "demagnetizing". We've been through that topic several times in endless detail. Short answer: it depends on the cartridge and on who you ask, but active demagnetizing has ruined some cartridges so don't do that without researching first.